PubMed Health⌕ Search

Biomedical subjects

M I Sherman

Publications and source records attributed to M I Sherman.

89 records · Page 5Linked to original sources
PubMed1975

Delta5,3beta-hydroxysteroid dehydrogenase activities in rat trophoblast and ovary during pregnancy.

Delta5,3beta-Hydroxysteroid dehydrogenase (3beta-HSD) activity has been measured in homogenates of ovary and trophoblast from 9th to 21st day pregnant rats under conditions where there was little or no further metabolism of the progesterone formed from pregnenolone. Trophoblast 3beta-HSD activity is first detectable on the 11th day of gestation; the specific activity peaks on the 13th day, and falls thereafter. The ovary enzyme activity rises gradually to the 19th day and falls on the 21st day. Decidua homogenates contain very low levels of 3beta-HSD activity, while embryo and yolk sac homogenates do not posses significant amounts. Total 3beta-HSD activities were also determined on a per conceptus basis. At no time during pregnancy does the total trophoblast 3beta-HSD activity exceed 40% the activity of the ovary. This may explain why the progesterone-producing capacity of trophoblast in the rat is inadequate to support normal pregnancy following ovariectomy. The temporal patterns of trophoblast and ovary 3beta-HSD activity suggest that the enzymes are not coordinately controlled in the two tissues.

Animals↗
PubMed1975

Effects of bromodeoxyuridine, cytosine arabinoside and Colcemid upon in vitro development of mouse blastocysts.

Mouse blastocysts in culture have been treated with increasing concentrations of cytosine arabinoside, bromodeoxyuridine or Colcemid. Concentrations of all three antimetabolites have been found which interfere with neither hatching of the blastocysts from their zona pellucidae nor subsequent attachment of the blastocysts to the culture dish, but which eventually result in death of the inner cell mass (ICM) and its derivatives. The effect upon the ICM is selective at these antimetabolite concentrations since many or, in some cases, all trophoblast cells continue to survive, and by a number of criteria, undergo normal patterns of differentiation and development.

Animals↗
PubMed1972

Detection of maternal esterase in mouse embryonic tissues.

A genetic variant of esterase in mice is used to demonstrate for the first time that an enzyme of maternal origin is taken up intracellularly by two mid-gestation tissues dervied from the embryo: trophoblast and yolk sac (visceral endoderm). Although other alternatives are still possible, it is likely that the esterase is transported from the mother to the trophoblast via the serum. If so, the phenomenon is selective, since at least one other prominent serum esterase is not found in trophoblast or yolk sac cells. The enzyme has not been detected in the embryo proper, even at very late stages of pregnancy. Trophoblast cells-developing from blastocysts implanted under the kidney capsule of a male mouse also appear to have the ability to take up host esterase. Efforts to demonstrate uptake of the enzyme by trophoblast cells in blastocyst cultures have been unsuccessful.

Animals↗
PubMed1969

The role of ribosomal conformation in protein biosynthesis: the streptomycin-ribosome interaction.

The role played by ribosomal conformation in codon-anticodon recognition has been studied using streptomycin as a probe, inasmuch as streptomycin is known to cause misreading of the genetic code. Changes in ribosomal structure have been followed by the method of hydrogen-tritium exchange. The results show that streptomycin induces two types of change in the hydrogen exchange pattern. At low molar ratios of streptomycin to ribosomes, a stimulation of the hydrogen exchange rate ("loosening" of ribosomal structure) is observed, with a small inhibition of polypeptide synthesis. As the streptomycin: ribosome ratio is increased, a maximum exchange rate is reached, after which the rate decreases ("tightening" of structure); in this region, inhibition of peptide synthesis increases sharply, and misreading of the code begins. None of these effects is observed with streptomycin-resistant ribosomes.

Escherichia coli↗